Ignition system



A ril 23, 1963 R. L. koNoPA IGNITION SYSTEM Filed March 15, 1961INVENTOR. Richard L. Konopa BY (LR W His A fiomey United States Patent3,087,090 IGNITION SYSTEM Richard L. Konopa, Anderson, Ind., assignor toGeneral Motors Corporation, Detroit, Mich., a corporation of DelawareFiled Mar. 13, 1061, Ser. No. 95,162 15 Claims. (Cl. 315-205) Thisinvention relates to ignition systems for internal combustion engineswherein a semiconductor such as a transistor controls current flow tothe primary winding of an ignition coil.

One of the objects of this invention is to provide an ignition systemwherein a semiconductor such as a transistor controls current flow tothe primary winding of an ignition coil and wherein the conduction ofthe semiconductor is controlled by voltage generating means driven insynchronism with the engine.

Another object of this invention is to provide an ignition systemwherein a semiconductor such as a transistor controls an ignitioncircuit and wherein the turning off of the semiconductor is accomplishedby a voltage developed across a capacitor.

Still another object of this invention is to provide an ignition systemwherein a transistor controls current flow to the primary winding of anignition coil, the transistor being biased normally conductive and beingturned oif at a periodic rate by a voltage developed on a capacitorwhich is connected with the transistor at the right time in the enginecycle through a circuit that includes another transistor whoseconduction is varied in synchronism with operation of the engine.

A further object of this invention is to provide an ignition systemwherein a transistor controls current flow to the primary winding of anignition coil, the transistor being normally biased on and being turnedoff by an RC timing circuit which is in turn controlled by means drivenin synchronism with an engine. 8

Further objects and advantages of the present invention will be apparentfrom the following description, refreence being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

The single FIGURE drawing is aschematic circuit illustration of anignition system made in accordance with this invention.

Referring now to the drawing, the reference numeral 10 designates aninternal combustion engine having eight spark plugs each designated byreference numeral 12 for firing the combustible mixture of the engine.It can be seen that one side of the spark plugs is connected directly toground whereas the opposite side of the spark plugs is connected withcontacts 16 on a distributor cap 14. The distributor rotor contact isdesignated by reference numeral. 18 and this contact is driven insynchronism with the engine to connect the lead wire 20 with each of thecontacts 16 as the rotor contact 18 rotates. The lead wire 20 isconnected with the secondary winding 22 of an ignition coil which isgenerally designated by reference numeral 24; The ignition'coil has aprimary winding 26, and it is seen that the primary and secondarywindings are connected at junction 28. The junction 28 is connected toone side of a resistor 30, the opposite side of thisresistor beingconnected directly to ground.

The primary winding' 26 of ignition coil 24 is connected with a leadwire 31. The lead wire 31 is connected to one side of a semiconductorswitch means which in this case takes the form of a PNP transistordesignated by reference numeral 32. It can be seen that the collectorelectrode of transistor 32 is connected with lead wire 31 whereas theemitter electrode of transistor 32 is connected with the lead wire 34.The base electrode of transistor 3 2 is connected with a junction 36 anda resistor 38 is connected between junction 36 and ground. The junction36 is connected to one side of capacitors 40 and 42. The opposite sideof capacitor 40 is connected with the junction 44. The opposite side ofcapacitor 42 is connected to ground as shown. The junction 44 isconnected with the collector electrode of a PNP transistor 46. Thisjunction 44 is also connected to one side of resistor 48, the oppositeside' of this resistor being grounded. The emitter electrode oftransistor 46 is connected with junction 50 and the base electrode oftransistor 46' is connected with junction 52. A resistor 54 is connectedbetween junctions 52 .and 56.

The ignition system of this invention includes a transistor 58 of theNPN type having base, collector and emitter electrodes. It isseen thatthe emitter electrode of transistor 58' is connected directly to groundwhereas the collector electrode is connected to one side of resistor 60.The base electrode of transistor 58 is connected with junction 62 and itis seen that this junction is connected to one side of capacitor 64 anddiode 66. The opposite side of diode 66 isconnected directly to ground.

The capacitor 64 has one side thereof connected with resistor 68, theopposite side of this resistor being connected with junction 70. Thejunction 70 is connected to the collector electrode of a PNP transistor72 and is also connected to one side of resistor 74. The opposite sideof resistor 74 is connected directly to ground. The emitter electrode oftransistor 72 is connected with the junction 76 whereas the baseelectrode of transistor 72 is connected with. a coil winding 78 whichforms a part of a magnetic pick-up device.

The coil winding 78 has voltage pulses induced therein whenever thetoothed rotor 80 rotates relative to the core member 82 uponwhich' thecoil winding 78 is wound. This magnetic device may take many forms, andas an example, the magnetic flux may be produced by a permanentmagnetand the flux passes through the rotor 80 and into the core 82 andthen returns back to an opposite side of the permanent magnet. Thedetails of construction of this device are not important to thisinvention, it only being necessary that pulses of voltage are generatedin the coil winding 78 as the rotor 80 rotates. The rotor 80 is drivenby the engine 10 so that there will be eight pulses of voltage inducedin the coil winding 78 for every revolution of the rotor 80. It ispointed out here that other devices could be used for controlling thisignition circuit, it only being necessary that some device be operatedin synchronism with the engine 10 for varying the conductivity oftransistor 72.

It is seen that the coil winding 78' is connected between the base andemitter electrodes of transistor 72. Itis also seen that one side of thecoil winding 78 is connected with the lead wire 34 which forms a commonconnection for the junctions 50, 56, 84,v and 76. The junction 84isconnected to one side of an ignition switch 86, the opposite side ofthis switch being connected to a voltage source 88- which in thisparticular case is a battery. The opposite: side of the DC. voltagesource 88 is grounded. as shown.

In describing. the operation of the ignition system, let itiirst'beassumed-that the teeth in rotor 80 are not in alignment with core 82 sothat there isno voltage induced in the coil winding 78. When there is novoltage generated in the coil winding 78, the transistor 72 will besubstantially fully nonco'nductive between its-emitter and collectorsince its emitter and base electrodes willbe at substantially the samepotential due to their connection through the coil winding 78. Sincethere is nov emitter to collector current flow in transistor 72, thereresult of this, the transistor 46 will be substantially fullynonconductive between its emitter and collector electrodes. The emitterand base electrodes of transistor 46 are at substantially the samepotential since they are connected by the resistor 54.

Since transistor 46 is now substantially fully nonconductive betweenemitter and collector, it can be seen that junction 44 will besubstantially at ground potential. It is also seen that one side ofresistor 38 is always connected to ground. Under these conditions, itcan be seen that there is a path for emitter to base current fortransistor 32 via the emitter electrode of this transistor, throughjunction 36 and through resistor 38 to ground. As a result of this basecurrent flow, there will be a much larger emitter to collector currentthrough transistor 32, and transistor 32 will therefore be turnedsubstantially fully on. With transistor 32 on between emitter andcollector, it can be seen that a large current flow will exist in theprimary winding 26 of the ignition coil 24. This circuit is from thepositive side of battery '88, to junction 84, through lead wire 34,through the emitter-collector circuit of transistor 32, through leadwire 31, through the primary winding 26 and thence through the resistor30 to ground. The magnetic field in the ignition transformer 24 willtherefore build up.

It is pointed out that when the transistor 32 is conducting between theemitter and collector, the capacitor 40 is being charged by the emitterto base current flow. The capacitor 40 will be changed from lead wire34, through the emitter to base circuit of transistor 32, throughcapacitor 40, and through resistor 48 to ground. The time that it takesto fully charge the capacitor 40 is determined by the RC time constantof the resistor 48 and capacitor 40.

In summarizing the conductive conditions of the transistors when thereis no voltage generated in the coil winding 78, it is seen thattransistors 72, 58 and 46 are nonconductive in their emitter-collectorcircuits. Transistor 32, on the other hand, is conductive betweenemitter and collector and also serves to charge the capacitor 40 throughthe emitter to base circuit of transistor 32. It is also apparent thatthe magnetic field is now building up in the ignition coil 24 and if thetransistor 32 were now suddenly made nonconductive, a large voltagewould be induced in the secondary winding 22 which would be applied to aspark plug 12 through the rotor contact 18 and one of the distributorcontacts 16.

As the rotor 80 continues to rotate, the time will come when one of itsteeth will be aligned with the core 82 and avolta-ge will therefore beinduced in the coil winding 78. The voltage that is induced in the coilwinding 78 is of such a polarity as to drive the base of transistor 72negative with respect to the emitter. This will, of course, cause anemitter to base current in transistor 72 which will turn transistor 72fully on between its emitter and collector electrodes. As a result ofthis, transistor 72 turns fully on and the junction 70 will now besubstantially at positive battery potential since it is connecteddirectly to junction 84 via the turned on transistor 72. With junction70 at a positive potential, the transistor 58 .will be turned on betweenits collector and emitter circuit. This is due to the fact that thepositive potential of junction 70 causes a base current to flow intransistor 58 that charges the capacitor 64. The time that this basecurrent will flow is determined by the RC time constant of 4 resistor 68and capacitor 64. Transistor 58 will therefore be turned on betweencollector and emitter until the capacitor 64 has been fully charged.When the capacitor 64 has been fully charged, the transistor 58 isswitched 01?.

When transistor 58 conducts between collector and emitter, it can beseen that there will be a base circuit for transistor 46 via resistor60, and the collector to emitter circuit of transistor 58. With basecurrent flow in transistor 46, the transistor is turned fully on betweenemitter and collector so that the junction 44 is now changed from groundpotential to the positive potential of the battery 88. With the junction44 substantially at positive battery potential, a discharge path forcapacitor 40 is set up via the emitter to collector circuit oftransistor 46. This capacitor will discharge via a circuit that includesthe resistor 38, battery 88, lead wire 34, and the emitter-collectorcircuit of transistor 46. It can be seen that the voltage that appearsacross the capacitor 40 will now be impressed across the emitter andbase electrodes of transistor 32 through the emitter to collectorcircuit of transistor 46. The polarity of the voltage on capacitor 48 issuch that the base electrode of transistor 32 suddenly becomes positivewith respect to the emitter. This will cause the transistor 32 to shutoff between emitter and collector and therefore cuts off the currentflow to primary winding 26.

The sudden turning off of the current flow between the emitter andcollector electrodes of transistor 32 and the stopping of current flowthrough the primary winding 26 causes a large voltage to be induced inthe secondary winding 22 which is applied to a given spark plug 12 viathe rotor contact 18 and one of the distributor cap contacts 16. Thiscauses a given spark plug 12 to fire. The time that the transistor 32 isturned off depends upon the RC time constant of resistor 38 andcapacitor 48 since the capacitor discharges through the resistor 38.When the capacitor 40 has completely discharged, there is no longer areversed biased condition on the transistor 32 so that it now will beonce more fully conductive between emitter and collector due to its basecircuit through resistor 38.

Referring back to the part of the circuit that includes resistor 68 andcapacitor 64, it is seen as has been previously described that thetransistor 58 remains conductive as long as the capacitor 64 ischarging. It is also seen that transistor 72 will remain fullyconductive between emitter and collector as long as there is a voltagebeing developed in coil winding 78. When the rotor rotates suflicientlyso that there is no voltage generated in coil winding 78, the transistor72 once more will be rendered nonconductive and the capacitor 64 willthen discharge through a circuit that includes resistors 68 and 74 andthe diode 66. The system is now ready for another voltage pulse in coilwinding 78 to set into motion a series of events which will once moreout off transistor 32.

The resistor 30 is provided in the circuit to limit the current flowthrough the emitter to collector circuit of transistor 32 to a safevalue. The capacitor 42 is intended to delay the turning off of thetransistor 32 to some extent and the circuit will have a sharper cut-oficharacteristic if the capacitor 42 is eliminated. Its provision howeverresults in a decreased spike in the primary voltage, waveform and animproved output. The resistor 54 is provided to prevent thermal run awayof transistor 46 under conditions of no base current since it acts totie the base to the emitter of this transistor during oif conditions oftransistors 58 and 32.

Although a magnetic pick up device has been shown for controlling theconductivity of transistor 72, it will be apparent to those skilled inthe art that other devices might be used to control the conduction oftransistor 72 in synchronism with operation of the engine withoutdeparting from the scope and spirit of this invention.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. An electrical ignition system for an internal combustion engine,comprising, a source of voltage, a spark discharge device, an ignitioncoil having a primary winding and a secondary winding, means connectingsaid secondary winding with said spark discharge device, a firsttransistor having emitter, collector and base electrodes, meansconnecting the emitter-collector circuit of said first transistorbetween said voltage source and the primary Winding of said ignitioncoil, a capacitor, a charging circuit for charging said capacitor fromsaid voltage source including the emitter-base circuit of said firsttransistor and a first resistor, a second transistor having emitter,base and collector electrodes, means connecting the emitter electrodesof said transistors together, a discharging circuit for said capacitorincluding the emitter-collector circuit of said second transistor and asecond resistor connected between one side of said source of voltage anda junction that is connected between one side of said capacitor and thebase electrode of said first transistor, and means for applying avarying voltage applied to the base electrode of said second transistorin synchronism with operation of said engine.

2. An ignition system for an internal combustion en.- gine comprising, asource of voltage, a spark discharge device for igniting the combustiblemixture of said engine, a first transistor for controlling theenergization of said spark discharge device having base, collector, andemitter electrodes, a second transistor having emitter, base andcollector electrodes, an RC timing circuit including a series connectedresistor and capacitor connected between the collector electrode of saidsecond transistor and the base electrode of said first transistor, apick-up coil connected across the emitter and base electrodes of saidsecond transistor, and magnetic means driven in synchronism with saidengine for causing pulses of voltage to be induced in said pick-up coilin synchronism with operation of engine.

3. An ignition system for an internal combustion engine, comprising, asource of voltage, a spark discharge device for igniting the combustiblemixture of said engine, a first transistor for controlling theenergization of said spark discharge device, a second transistor, an RCtiming circuit including a series connected resistor and capacitorconnecting the collector electrode of one of said transistors with thebase electrode of the other of said transistors, means for controllingthe conductivity of said second transistor in synchronism with operationof said engine, and a discharge circuit for the capacitor of said RCtiming circuit including a diode.

4. A control circuit for controlling the firing of an ignition circuitcomprising a first transistor, a second transistor, and RC networkincluding a series connected resistor and capacitor connecting the baseelectrode of one of said transistors with the collector electrode of theother of said transistors, and a pick-up coil connected across theemitter and base electrodes of one of said transistors.

5. An ignition system for an internal combustion engine comprising, asource of voltage, an ignition coil having a primary winding and asecondary winding, a spark discharge device, means connecting thesecondary winding of said ignition coil with said spark dischargedevice, a first transistor having its emitter-collector circuit connected between said voltage source and the primary winding of saidignition coil, a second transistor having emitter, collector and baseelectrodes, a capacitor connecting the collector electrode of saidsecond transistor with the base electrode of said first transistor, abase circuit for said second transistor including the emitter-collectorcircuit of a third transistor, a fourth transistor having emit ter,collector and base electrodes, an RC network including a seriesvconnected resistor and capacitor connecting the collector electrode ofsaid fourth transistor with the base electrode of said third transistor,and means con nected across the emitter and base electrodes of saidfourth transistor for varying its conductivity in synchronism withoperation of said engine.

6. An ignition system for an internal combustion engine comprising, asource of voltage, an ignition coil having a primary winding and asecondary winding, a spark discharge device connected with saidsecondary winding, a first transistor having its emitter-collectorcircuit connected between said voltage source and the primary winding ofsaid ignition coil, a second transistor having emitter, collector andbase electrodes, a capacitor connecting the collector electrode of saidsecond transistor with the base electrode of said first transistor, abase circuit for said second transistor including the emitter-collectorcircuit of a third transistor, a fourth transistor having emitter,collector and base electrodes, an RC network including a seriesconnected resistor and capacitor coupling the collector electrode ofsaid fourth transistor with the base electrode of said third transistor,a pick-up coil connected across the emitter and base electrodes of saidfourth transistor and means driven in synchronism with said engine forcausing voltage pulses to be generated in said pick-up coil.

7. An ignition system for an internal combustion system comprising, avoltage source, a spark discharge device, an ignition coil having aprimary winding and a secondary winding, means connecting said secondarywinding with said spark discharge. device, a first transistor havingemitter, collector and base electrodes, means connecting theemitter-collector circuit of said first transistor, between said powersource and the primary winding of said ignition coil, a secondtransistor having emitter, base and collector electrodes, meansconnecting the emitter-collector circuit of said second transistoracross said voltage source, a capacitor connecting the collectorelectrode of said second transistor with the base electrode of saidfirst transistor, a third transistor having its emitter-collectorcircuit connected between the base electrode of said second transistorand one side of said power source, a fourth transistor having emitter,collector and base electrodes, means connecting the emitter-collectorcircuit of said fourth transistor across said power source, an RCnetwork connecting the collector electrode of. said fourth transistorwith the base electrode of said third transistor, a diode connectedbetween the base electrode of said third transistor and one side of saidpower source, a pick-up coil connected across the emitter to basecircuit of said fourth transistor and means driven in synchronism withsaid engine for causing voltage pulses to be generated in said pick-upcoil.

8. An ignition system for an internal combustion engine comprising, asource of voltage, an ignition coil having a primary winding and asecondary winding, a spark discharge device for igniting the combustiblemixture of said engine, means connecting said secondary winding withsaid spark discharge device, a transistor controlling a circuit for saidprimary winding, a capacitor, 21 charging circuit for said capacitorincluding the emitter-base circuit of said transistor, variableconducting means, a discharging circuit for said capacitor includingsaid variable conducting means, a point on said discharging circuitbeing connected with the junction of the base electrode of saidtransistor and one side of said capacitor and with one side of saidsource of voltage, and means for operating said variable conductingmeans in synchronism with said engine.

9. A timing circuit for an internal combustion engine ignition systemcomprising, a source of voltage, a transistor having emitter, collectorand base electrodes, a capacitor, a charging circuit for said capacitorincluding the emitter-base circuit of said transistor, variableconducting means operated in synchronism with said engine, a dischargingcircuit for said capacitor including said variable conducting means anda conductive circuit that connects one side ofsaid capacitor and thebase electrode of said transistor with one side of said source ofvoltage.

10. A timing circuit for an internal combustion engine ignition systemcomprising, a source of voltage, first semiconductor switch means havinga pair of current carrying terminals and a control terminal, meansconnecting said current carrying terminals across said source ofvoltage, second semiconductor switch means having a pair of currentcarrying terminals and a control terminal, means connecting the currentcarrying terminals of said second semiconductor switch means across saidpower source, a capacitor connecting the control terminal of said firstsemiconductor switch means with one of the current carrying terminals ofsaid second semiconductor switch means, a charging circuit for saidcapacitor including the control terminal and one of the current carryingterminals of said first semiconductor switch means, a dischargingcircuit for said capacitor including the current carrying terminals ofsaid second semiconductor switch means and a conductive circuit whichconnects one side of said capacitor and the control terminal of saidfirst semiconductor switch means with one side of said source ofvoltage, and means driven by said engine for controlling said secondsemiconductor switch means.

11. The combination according to claim 10 wherein at least one of thesemiconductor switch means is a transister.

12. A timing circuit for an internal combustion engine ignition systemcomprising, a source of voltage, a first transistor having emitter,collector and base electrodes, -a second transistor having emitter,collector and base electrodes, a capacitor connecting the base electrodeof said first transistor with the collector electrode of said secondtransistor, a charging circuit for said capacitor including theemitter-base circuit of said first transistor, a discharging circuit forsaid capacitor including the emittercollector circuit of said secondtransistor and a conductive circuit which connects one side of saidcapacitor and the base electrode of said first transistor with one sideof said source of voltage, and means driven by said engine forcontrolling said second transistor.

13. A timing circuit for controlling an internal combustion engineignition system comprising, a source of voltage, a first transistorhaving emitter, collector and base electrodes, a second transistorhaving emitter, collector and base electrodes, means connecting theemitter-collector circuits of both of said transistors across saidsource of voltage, a capacitor connected between the base electrode ofsaid first transistor and the collector electrode of said secondtransistor, .a charging circuit for said capacitor including theemitter-base circuit of said first transistor and a circuit whichconnects the collector electrode of said second transistor with one sideof said source of voltage, and a discharging circuit for said capacitoroperative when said second transistor is conductive in itsemitter-collector circuit, said discharging circuit including theemitter-collector circuit of said second transistor and a circuit whichoonductively connects the base electrode of said first transistor withone side of said source of voltage. I

14. A timing circuit for an internal combustion engine ignition systemcomprising, a source of voltage, a first transistor having emitter,collector and base electrodes, a second transistor having emitter,collector and base electrodes, a capacitor, means connecting saidcapacitor be tween the base electrode of said first transistor and thecollector electrode of said second transistor, a charging circuit forsaid capacitor including the emitter-base circuit of said firsttransistor and a conductive circuit which connects the collectorelectrode of saidsecond transistor with one side of said power source,and a discharging circuit for said capacitor including theemitter-collector circuit of said second transistor and a conductivecircuit connecting the base electrode of said first transistor with oneside of said source of voltage.

15. A timing circuit for an internal combustion engine ignition systemcomprising, a first transistor having emitter, collector and baseelectrodes, a second transistor having emitter, collector and baseelectrodes, a source of voltage, a capacitor connected between the baseelectrode of said first transistor and the collector electrode of saidsecond transistor, a first resistor connecting one side of saidcapacitor and the collector electrode of said second transistor with oneside of said source of voltage, and a second resistor connecting anopposite side of said capacitor and the base electrode of said firsttransistor with the same side of said voltage source, said firstresistor and the emitter-base circuit of said first transistor formingpart of a charging circuit for said capacitor, said second resistor andthe emitter-collector circuit of said second transistor forming a partof a discharging circuit for said capacitor.

References Cited in the file of this patent UNITED STATES PATENTS2,953,719 Guiot Sept. 20, 1960 FOREIGN PATENTS 1,211,857 France Oct. 12,1959

1. AN ELECTRICAL IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE,COMPRISING, A SOURCE OF VOLTAGE, A SPARK DISCHARGE DEVICE, AN IGNITIONCOIL HAVING A PRIMARY WINDING AND A SECONDARY WINDING, MEANS CONNECTINGSAID SECONDARY WINDING WITH SAID SPARK DISCHARGE DEVICE, A FIRSTTRANSISTOR HAVING EMITTER, COLLECTOR AND BASE ELECTRODES, MEANSCONNECTING THE EMITTER-COLLECTOR CIRCUIT OF SAID FIRST TRANSISTORBETWEEN SAID VOLTAGE SOURCE AND THE PRIMARY WINDING OF SAID IGNITIONCOIL, A CAPACITOR, A CHARGING CIRCUIT FOR CHARGING SAID CAPACITOR FROMSAID VOLTAGE SOURCE INCLUDING THE EMITTER-BASE CIRCUIT OF SAID FIRSTTRANSISTOR AND A FIRST RESISTOR, A SECOND TRANSISTOR HAVING EMITTER,BASE AND COLLECTOR ELECTRODES, MEANS CONNECTING THE EMITTER ELECTRODESOF SAID TRANSISTORS TOGETHER, A DISCHARGING CIRCUIT FOR SAID CAPACITORINCLUDING THE EMITTER-COLLECTOR CIRCUIT OF SAID SECOND TRANSISTOR AND ASECOND RESISTOR CONNECTED BETWEEN ONE SIDE OF SAID SOURCE OF VOLTAGE